In the past, techniques for converting electromagnetic energy, such as, solar energy, to electrical or to mechanical energy usually involved a flat plate collectors wherein fluids or gases were circulated to carry away the heat energy thus received. These solar collectors absorbed energy only in the near and far infrared spectrum leaving much of the visible spectrum unavailable for heat production. Moreover, these systems generally did not use the generated heat for driving electro-mechanical devices, such as, turbines and generators.
Rhodes discloses, in U.S. Pat. No. 4,084,577, a solar converting apparatus wherein halogens such as iodine or bromine are introduced into a sealed enclosure and irradiated with solar energy. The solar energy is converted to heat and utilized to heat a fluid passing through a pipe. There is no teaching of how such converted energy could be directly used to drive an electro-mechanical device such as a turbine or generator.
In U.S. Pat. No. 2,969,637, Rowekamp discloses a system for converting solar energy into mechanical energy. A volatile liquid such as dichloro-difluoro-methane is heated by means of exposure to sun rays with the resulting expansion of gases passing through a turbine having a shaft connected to the armature of an electrical generator. A disadvantage of this system is that dichloro-difluoro-methane has very limited absorption in the visible region, this material could not be used to absorb solar energy directly. The prior art process basically consists in a system of piping which is exposed to the sun. The piping heats the volatile liquid contained therein by conduction.
U.S. Pat. No. 4,376,372, to English, also discloses a solar collector in which pipes containing liquid are heated to collect solar energy. U.S. Pat. No. 4,068,474to Dimitroff, discloses an apparatus based on similar principles in which solar radiation is focused on the head of a conductor which, in turn, heats water to produce steam. Yet another such process is disclosed in U.S. Pat. No. 4,158,354, in which the heat exchanging fluid is ammonia.
Still further efforts to derive power from solar energy are disclosed in U.S. Pat. Nos. 3,998,205, 4,024,715, 4,026,112, 4,175,381 and 4,426,354. Such additional efforts have certain drawbacks. For instance, fuel and oxidants are required for generating power from solar radiation. Also, additional processing steps are oftentimes required.